1. Field of the Invention
This invention relates to internal combustion engines wherein most or all of the compression is done outside of the working cylinders, with a variable compression ratio compressor and with direct regeneration of exhaust heat to the compressor outlet gas.
2. Description of the Prior Art
Practical internal combustion engines have three basic functions to perform: (1) Compression of air (or air/fuel mixture or air/fuel/exhaust mixture or air/exhaust gas mixture), (2) provide a combustion process (burning or explosion) of a fuel/oxidizer mixture, and (3) expansion of the hot combustion products against a mechanical device (e.g. piston) to produce useful work. A basic efficiency conflict exists in the three functions. The compression needs to be carried out in a cold chamber but the combustion and expansion functions require a hot chamber (insulated so that valuable heat is not lost to the surroundings).
Gas turbine technology solves this conflict by physically separating the compressor from the burner and from the work expander (turbine). Thus, the compressor can be cooled while the burner and turbine can be insulated.
The early days of engine development were governed by different problems than those of today. Fuel (particularly gasoline) was cheap and plentiful and therefore high efficiency was not essential. Strong materials were not available and the total weight allotted to the engine was comparably small. Thus, the overriding constraint was compactness and total size; this was in direct opposition to the gas turbine approach that spread everything out. The Otto and diesel concepts fit the bill in those early days. Everything was compact such that one working chamber, not three (compressor, burner, expander), was required. The same cylinder was used to compress, burn and expand. A major loss in efficiency results from this concept of a single, multifunction chamber. The compression must be done in a hotter than desired chamber while combustion and expansion must be done in a colder than desired chamber.
Many U.S. patents teach compression external to the working cylinders, see for example: U.S. Pat. Nos. 682,567; 914,566; 1,114,521; 1,305,580; 2,769,435; 2,799,258; 2,873,574; 3,148,668; 4,040,400. If only part of the compression is done externally, the process is called super-charging. If substantially all of the compression is done external to the working cylinders, the previous art teaches additional cylinders in the main engine block reserved for compression only. A portion of the cycle time is allotted to transferring compressed gas from the compression cylinders to the working cylinders. These approaches are not adequate solutions to the problems faced today.
Applicant's copending patent application Ser. No. 970,320, filed Dec. 18, 1978 entitled INTERNAL COMBUSTION ENGINE describes the use of external compression, variable compression ratio, and direct exhaust regeneration in an Otto cycle. An extensive optimization theory is presented in that copending patent application. Prior art (Otto and diesel) cycles do not permit direct regeneration due to the prohibitive penalty in work of compression.
The present invention takes into account the prior art diesel type cycle. The term diesel "type" cycle is used here because the classic concepts and definitions inherent in the terms "Otto" and "diesel" do not accurately and completely describe the present invention nor that of said copending application Ser. No. 970,320, filed Dec. 18, 1978. The present invention presents a more realistic, practical, and accurate model of the unit processes taking place in an internal combustion engine of the type considered here. It is to be understood that the classical Otto and diesel cycles (idealized) extensively analyzed in the literature represent special, degenerate cases of the present model. Applicant's copending patent application Ser. No. 970,320, filed Dec. 18, 1978 analyzes extensively the modified Otto type cycle and the present patent application analyzes the modified diesel type cycle as well as the generalized cycle.
It is an object of the present invention to optimize the design of an internal combustion engine. This includes spark ignition engines, compression ignition engines, exhaust heat ignition engines, and combinations of these.
It is another objective of this invention to greatly improve the efficiency of an internal combustion engine and therefore the mileage of a vehicle using such engine and therefore to greatly reduce oil consumption.
It is another object of this invention to perform most or all of the compression outside of the working cylinder of an internal combustion engine and to vary the compression ratio in response to changes in certain parameters.
It is another object of this invention to provide an internal combustion engine with direct regeneration of exhaust heat.
It is another object of this invention to provide a definite relationship between the compressor output pulsations and the power cycles in the working cylinders. This relation may be cyclic, slowly changing, fixed, controlled, or random (surge tank between compressor and cylinder inlets).